The terms 'nervous breakdown' and 'mental breakdown' are not formally defined in a diagnostic system such as the DSM-IV or ICD-10. The terms are not often used in the scientific literature on mental illness.[1][2]

Specific cases are sometimes described as a 'breakdown' only after a person cannot function in day-to-day life.[3]

Causes of such breakdowns are varied. A study found that problems with intimate relationships, such as divorce or separation, contributed to 24% of nervous breakdowns.[4] Problems at work and school accounted for 17% of cases, and financial problems for 11%. Surveys suggest that in the United States, health problems have decreased in importance as a contributor to nervous breakdowns, as these accounted for 28% of nervous breakdowns in 1957, 12% in 1976, and only 5.6% in 1996.[4]

In themselves, nervous breakdowns are considered a 'health problem' by most professionals.